Skip welding control



April Filed March 3, 1949 14, 1953 s. MA SPICE ET A1.

SKIP WELDING CONTROL 5 Sheets-Sheet l Inventors w 752e zzzzg (ItlornegsApril 14, 1953 s. M SPICE ET Al. 2,635,165

SKIP WELDING CONTROL Filed March 5, 1949 5 Sheets-Sheet 2 E Wzlw www@'@WWU] Gttorncgs April 14, 1953 s. M SPICE ET AL 2,635,165

SKIP WELDING CONTROL.

Filed'Maroh 3, 1949 3 Sheets-Sheei 5 OFF TIME TIME l l all if 41'/ 2 r(ttornegs Patented Apr. 14, 1953 UNITED STATES PATENT OFFICE Wilbur E.Moehring, Flint, Mich., assignors to General Motors Corporation,Detroit, Mich., a

corporation of Delaware Application March 3, 1949, Serial N o. 79,462

12 Claims.

This invention relates to welding control means and more specifically toa compound control system for actuating a submerged melt intermittentlyor what might be termed a skip welding process. Various types ofequipment have been common for continuously welding two parts togetherwhich are in juxtaposition over a relatively long distance. For example,during war production large metal sheets were welded together by variousmeans including submerged arc welding, which sheets were injuxtaposition for some considerable distance, along the junction line ofwhich the two were to be welded together. As long as the partsthemselves were relatively heavy or thick in section, the amount of heatintroduced into the same from welding was not injurious, but where thesections b ecame thinner and the parts large in area in comparison totheir thickness. the introduction of localized heating from welding wasfound to have injurious effects such as warping or twisting. As anexample of such a disadvantage or diiculty, if it were desired to secureto a relatively thin disc or plate a toothed rim of considerabljrthicker section by welding, and the inner edge of the rim were to bewelded to the anged periphery of the disc or plate, the heat from saidcontinuous weld might readily be suificient to warp the plate so thatthe combined resulting wheel would not be flat, but would be warped orwavy. In order to alleviate such difficulties and to still secure partstogether, a discontinuous or skip welding method was tried so that alongthe total length of the juxtaposed parts, instead of having a continuouslong weld, a series of spaced short welds would be used. This method wasutilized to secure a relatively thick toothed rim to a flanged discplate and it was found that the reduction in total heat, as well as thespaced heated intervals, was sufficient to spread out the heating and toreduce the same so that there was no appreciable warpage of theresulting wheel.

In order, however, to provide an automatic system of this type, it is.of course, necessary to provide control means for causing relativemotion between the parts to be welded together and the weldingelectrode, feeding the electrode toward the work at proper times andproper speeds and then discontinuing said feeding, and to control thevoltage or power between the electrode and the work at certainpredetermined time intervals.

It is, therefore, an object of our invention to provide a weldingcontrol system Vior producing a series of discontinuous spaced welds atthe junction plane of parts to be secured together.

It is a further object of our invention to provide control means forfeeding an electrode with respect to the work and controlling the timedvoltages thereon to, in the end result, provide a series of intermittentskip welds to secure two parts together.

It is a further object of our invention to provide control means forfeeding the electrode with respect to the work at different rates atdifierent timed portions of the operating cycle.

It is a further object of our invention to provide such a controlcircuit that the welding current between the welding electrode and thework is maintained for a short period of time following the cessation ofelectrode feed to burn off the electrode to prevent sticking.

It is a still further object of our invention to provide a controlsystem which is adjustable to provide dilerent lengths of weld toaccommodate diierent circumstances of securing by welding.

It is a still further object of our invention to provide a controlcircuit in which timing means is provided for the individual welds aswell as an overall control time for the whole operation.

With these and other objects in View which will become apparent as thespeciiication proceeds, our invention will be best understood byreference to the following specilication and claims and theillustrations in the accompanying drawings` in which:

Figure 1 discloses a schematic wiring diagram showing a portion of thecontrol circuit of our invention;

Figure 2 shows a schematic wiring diagram of the remainder of thecontrol system of our invention. the two parts of the system cooperatingtogether to provide the complete control; and

Figure 3 is an oscillograph chart showing the simultaneous voltages inthe wire feed motor armature and across the arc.

It will become evident as the specific disclosure proceeds that thereare a number of different relay coils which control one or more sets ofrelay contacts which, for purposes of clarification in the drawings. areshown at a point removed from the operating coil, and in order toclearly and simply define each coil with its operated contacts, theywill be hereinafter referred to by the same reference characters butwith subnumerals. For example, assuming that a relay coil operated aplurality of contacts, the relay coil per se will be identified, forexample, as CR-l,

whereas the contacts operated thereby will be referred to as CR-h andClt-2z. Further, in order to assist the identification of the contactswith their operating coil, dash and dotted arrow lines have been drawnfrom the operating coil in the direction of its operated contacts andthe number of arrows emanating from any one coil indicates the number ofcontacts operated.

Referring now more specifically to said drawings, in Figure 1 there isshown a pair of main supply lines 2 and 6l, which are connected to theordinary 110 volt A. C. plant power. First in order from the upperportion of the drawings connected between these lines are a pair ofrelay contacts designated CR-l I2, one contact of which is connected toline 4 through line 6, the other contact being connected through line 8to operating solenoid coil lil and thence to the other supply line 2.The solenoid coil It is the operator for an air Valve i2 which controlsthe feed of the flux in this instance used to submerge the aro. Thisflux is maintained in a hopper not shown and fed down to the approximateposition of the portion to be welded at the time the arc is drawn. Inother words, when the relay contacts CR-llz are closed, and they areshown normally open, the ux will feed to the work. A line l, likewiseconnected to the main buss 4, extends to the primary on/oif switch i6,which is in turn connected to an overall timer I8, for controlling thetime of a complete welding operation to secure two parts together, theopposite terminal of which is connected through line 20 to main line 2.When the on/oif switch l is closed, therefore, the timer begins tooperate and will continue to time the definite interval at the end ofwhich the two parts are secured together by a plurality of skip weldsand, through certain means to be described, it will deenergize thesystem.

Conductor 22, extending from main line 4, is connected t0 normally openrelay contacts CR-21 and the opposite terminal thereof is connectedthrough line 2t to one end of relay coil CR-I, whose opposite endterminates at main line 2. Conductor 26 extends from main line i throughthe primary 23 of transformer 3B, the opposite terminal of which isconnected through line 32 to one side of primary 36 of transformer 36,and thence through line 38 back to main line 4. Line 33 is alsoconnected to one end of primary 4B of transformer 42, the opposite sidebeing connected through conductor fili -to main line 2. The secondary 43of transformer 35 is connected in series with secondary i8 oftransformer 42, the latter being connected directly to the control grid50 of a triode tube 52. The secondary 4B is likewise connected throughconductor 54 to an interval timer circuit consisting of a resistor 56 inparallel with a variable condenser 58, the opposite terminal of which isgrounded. Thus, by varying the capacitor 53, the RC characteristics arevaried and the time period of the system is changed. The plate 60 of thecontrol tube 52 is connected through line 62 to secondary 64 oftransformer 3|! and thence through line |53 to relay coil CR-2, theopposite terminal of which is grounded. The capacitor 68 is connected inparallel around coil CBL-2. Conductor lil is connected between line 32and normally closed contacts CR-|1, the opposite contact being connectedthrough line l2 to a pair of normally open contacts ifi, operated by theoverall timer i8. These contacts are likewise connected through line 'I6to main line 2.

Next in order is a control line for relay CR-3 and consists of conductor73 connected to normally open relay contacts CR-tr, thence throughconductor 8D to normally closed relay contacts CR-Bi, and continuingthrough conductor 82 to relay coil CR-a, terminating in main line 2.Conductor 85, connected to main line li, extends to a pair of normallyopen contacts CPU-l1, which are in turn connected through line 85 torelay coil CR-G, which terminates at main line 2. Conductor 88 extendsfrom main line f3 to a cam actuated switch Si), connected in turnthrough conductor S2 to relay contacts Clt-lh, and thence through line9@ to relay coil Clt-5, terminating in main line 2. In shunt relationaround contacts Clt-|01 is a spring biased push button switch 96 forshorting out this pair of contacts when desired, the object of thisswitch being to inch the table or move it slowly.

Conductor Sil, connected to main line extends to a normally open springbiased switch 98 of the so-called microswitch variety, which remainsopen unless pressure is maintained thereon to keep it closed. Theopposite terminal of this switch is connected through line it@ to relaycoil Clt-6, the opposite terminal of which extends to a pair of normallyclosed contacts CTR-51, and thence to main line 2. A set of normallyopen contacts CR-Zz are provided in shunt relation around themicroswitch 58 and a second pair of normally open contacts CR-Sz arealso connected in parallel therewith. Line |62, connected commonly toline |55 and one side of contacts Clt-22 and Clit-52, extends to primaryit@ of transformer IUS, and thence connected to a second primary |113 oftransformer il@ in series therewith, the latter terminating at main linefi. Secondaries and ||2 of transformers it@ and l respectively, are alsoconnected in series and thence to a resistance-capacity circuitincluding resistor l It and variable capacity lle in parallel, theopposite end of which is grounded, one terminal of secondary beingconnected through line H8 to the control grid l2@ of triode |22. Primarylt of transformer |25 is interconnected between line |E2 and one end ofcontrol relay CR-S. The plate |28 of tube |22 is directly connected tosecondary |39 of transformer |25 and thence through control relay coilCR-'i to ground, a capacitor |32 being placed in shunt relation aroundsaid coil. Conductor i3d extends from a common point between primariesits and me to main line 2.

Conductor |36, connected to main line li, is likewise connected to apair of normally open contacts CR-lz, the opposite side of which isconnected through line |38 to primary |45 of transformer |42, theopposite side of the transformer primary being connected directlythrough line mit to main line 2. Two transformers i' and |158, havingtheir primaries |55 and |52 connected in series between lines i and |38,likewise have their secondaries i5@ and |56 connected in series betweenan RC time circuit consisting of resistance |58 and variable capacitance|55 in parallel and control grid |62 of triode ld. Plate |55 of tube IBGis connected through conductor |53 and secondary 'it of transformer #i2to relay coil CR-i, the opposite terminal of which is grounded.Condenser |'|2 is connected in shunt around relay coil Clt-8. Conductorliti interconnects the intermediate point between the primaries l5@ and|52 and main line 2.

Conductor interconnects main line d with a set of normally open relaycontacts CR-Sa which are in like manner connected through line H8 toprimary I8@ of transformer 32, the opposite terminal of which isconnected through line l84 with main line 2. rlwo transformers l E6 andlli-8, having their primary coils i9@ and connected in series betweenlines 'lil and l likewise have their secondaries it@ and it@ connectedin series between an RC circuit consisting of resistance ld and variablecapacitor 236 in parallel and the control grid 262 ci tube 2cd. Theplate d of said tube 29d is connected through line 20S to secondary 2 i0of transformer 22 and thence through line 2l2 to control relay CR-S andto ground. A condenser 2M is connected i shunt across said relay coilCEc-2. Line ri is connected from a point intermediate the two primariesigt and 22 to main line 2. Connected directly across lines 2 and d isprimary 25S of transformer 228, secondary 222 of which provides a sourceof power for the heater filaments of the various tubes in the controlsystem.

Referring now more specifically to Figure 2, while the circuitconnections are discontinuous between Figure l and Figure 2, there is acrossrelationship in that certain of the operating' coils shown inFigure l control contacts in Figure 2 and vice versa. There is shown atthe top of this ligure a driving motor 225i which is adapted to drivethe body which is being welded relative to the welding head. This motormay be any one of a plurality of conventional driving motors and issupplied by power over a three-phase power line 22d, and controlled by aseries of ccn tacts (3R-51, CIR-52, CR-s, in each line, which arecontrolled, of course, by relay Clt-5. When these contacts are closed,the motor is operative to move the parts being welded. A 1.15 volt D. C.exciter armature is shown at 222, which provides control voltages tolines 23d The exciter is provided with a field coil 233 connected acrossthe armature. Connected across the control busses 23H3 and 232 is afield coil 233 of a small motor to feed the weld wire or rod withrespect to the work. The armature of this motor is also shown within thedotted outline indicating the wire feed motor, and is itself connectedin a circuit to be described.

The welder is shown at 23S and connected to two main lines 24d andConnected in shunt with the welder are a of normally closed contactsC-R-l1, a relay operating.r coil Clt-i3, and a pair of normally opencontacts MlL--L which are controlled by the main relay MR, all three ofthese elements being connect series in said shunt circuit. The mainlines and 242 which are connected to the welder extend to the weld wireor rod and work to provi-ile the are for welding which is indicated atpoint 2de. A shunt 2li@ is provided in line across which ammeter 25S isconnected to indicate the current flow. In like manner a voltmeter isconnected across the are to read instantaneous voltages. A conductor 252is comiectefil to line 2152 and extends directly to armature ci the wirefeed motor. The opposite terminal ci" said armature is connected throughline 25-1 to a pair or normally closed relay contacts Clt-t1. Theserelay contacts are likewise connected throueh line 255 to armature 25Sof a driven control exciter, the opposite terminal o which is connectedthrough line 25E to manually movable switch. arm 262 of one of the mainswitches. This arm 262 is adapted to contact three stationary contacts264, 265 and Contact 26d is connected first to a variable tappedresistor 219, secondly to al pair of normally open relay contacts CR-31and to one terminal of a manual push button switch 212. The oppositeterminal of the resistor 210 is directly connected to one of the relaycontacts CR-31, to normally open relay contacts CR-lSi, and to normallyopen relay contact CR-lZz. The opposite terminals of each of the lasttwo mentioned sets of contacts are directly connected through conductiveline 2M to the shunt 246 and likewise through resistor to the pushbutton switch 212. Center contact 256 is unconnected and stationarycontact 253 is directly connected through conductor 21S to armature 23%.

Arm 282 is one part of a multi-position multiarm main switch having twoother movable blades or contactors 280 and 282, which movesimultaneously therewith. When this combination switch is moved to itsupper position, as shown in Figure 2, the device is in position to weldand the welding wire (electrode) can oe moved down. When in its centerposition, the device is deenergized, and when in its lower position, thewelding wire raises up, all of which will be later explained in moredetail. Arm 28D of this combined switch engages two contacts which aremerely dummies, as they are not connected with any part of theapparatus. The third contact 284, however, has a conductive line 23Sconnected thereto which extends to a variable resistor 288, which isalso connected directly to control buss 232. It also extends to a pairof normally open relay contacts Clt-32, which are in turn seriallyconnected with a pair of normally open relay contacts MR2, and thence tomain control buss 23E). The excited ileld 29) is connected betweencontrol buss 232 and a variable adjuster tap 292 which engages theresistance 28B. The third switch arm 222, connected through line 28! tobuss 236, also engages three contacts, only one of which is connectedinto the circuit. That one, 294, is connected through line 256 to amanually operable switch 293, which is mechanically connected to andoperates with main switch l5, and thence through line 33B to a normallyclosed microswitch 322, which is cam operated, and further seriallythrough normally closed emergency stop switch 364. Conductor 325 thenextends from switch 3M to a pair or normally open relay contacts TDR-I1,which are operated by the time delay relay. Also connected to contactsTDR-l1, through conductive line 388, are a pair of normally open relaycontacts CIR-33. Conductor SIG likewise connects contacts CEL-33 to arelay coil FR of the iield relay, the other terminal of which isconnected to the control buss 232.

The main relay coil MR., having in series therewith a resistor isconnected in shunt around field relay FR and relay contact CR-33 inseries. In like manner relay coil CR-ID is connected in shunt around themain relay coil MR. Relay coil CR-i 2 is connected in shunt around relaycoil FR. Relay coil TDR-l is directly connected to control buss 232 andthence to a manual push button switch 312, the opposite terminal ofwhich is conductively connected to line 306. Relay coil CR-Il isconnected to main control buss 232 and thence through conductive line 3ld to one side of the push button switch SI2, to a pair of normally openrelay contacts CR-l l1, the opposite side of which is also connected toline 306 and which, oi course, act as holding contacts, and to one sideof a pair of normally open contacts Clt-B3. The opposite terminal ofcontact (1R-63 is connected through a switch 316 to line 306. A switch3H 7 in parallel with switch 238 is mechanically a part of switch 3 I 6,as indicated by the dotted line, and moves together therewith as adouble pole, double throw switch, closing one section and opening theother simultaneously.

Conductor 3 I 8 is connected to control buss 232 and extends to resistor32 0, which is serially connected to a variable resistor 322, which isconnected in series relation with a second fixed resistor 324 across tocontrol buss 230. The Welder eld 326 is directly connected to controlbuss 232 and thence to a variable resistor 328, which is seriallyconnected in turn to normally open relay contacts FE1, which are againserially connected to a second variable resistor 339, having itsopposite Contact connected to the other control buss 233. A crossconnection 332 extends from a point between resistor 328 and relaycontacts FE1 to a mid-point between resistor 320 and resistor 322.

In general it is emphasized that the control system is provided toproduce a series of intermittent spaced welds between two parts to besecured together or what might be termed skip welding. The particularconguration of the junction line between the parts may take any desiredform; the only design necessary is that in automatic welding the weldinghead must follow along the seam. After the welding electrode is broughtinto proximity to the work at the starting point, one complete cycle ofthe system consists in:

1. Welding current is applied and motion between the work and electrodeis started which relative motion is maintained throughout the completework period. The welding time is maintained to produce a specifiedlength of weld between the parts and during this time the weld rod iscontinuously fed toward the work and the flux is fed down to submergethe arc.

2. The feed for the weld rod is stopped but the welding current is lefton. 'I'his provides current to burn olf the end of the weld rod as thework moves along and produces a clean break at the end of thatparticular weld, and spaces the end of the rod from the work so that itwill not strike the work intermediate the weld areas.

3. Weld current is cut off.

4. A time delay period is provided to: (a) Enable the voltage supply forthe feed motor to decay and approach as nearly as possible the stablevoltage; and (b) To hold the wire spaced from the work until just priorto the next sequential weld.

5. Weld rod feed is energized to bring the weld rod down slowly intoengagement with the work again after which engagement is moves over thework for a short distance before the next application of welding currentand a repetition of the same cycle.

These cycles are repeated until the complete distance over which theseskip welds are to be applied has been covered and then the whole systemis deenergived.

With this general description of the operation in mind, reference willnow be made speciiically to the system for carrying out the same. Itwill be noted from the above general description that there are severaldifferent time intervals that have to be determined and set priortooperation. These are:

l. Ihe length of time the weld current shall remain on.

2. The burn oif time or that time during which the weld rod feed isstopped but the weld current is maintained on.

3. The delay time which determines the time period between the cessationof welding current and the initiation of weld rod feed for the nextweld.

The adjustable control circuits for all three are shown on the lowerhalf of Figure i.

The time control circuit for the first of these time intervals is formedby variable capacity H6 in circuit with resistor H4 to form anadjustable RC circuit for controlling tube l22 in whose output circuitis control relay CR-'L Thus, by adjusting capacitor H3, the length oftime the weld current is on may be varied. The time circuit for burn offtime is formed of variable capacitor |56, resistor |58, tube |64 andcontrol relay CRPS, and the time circuit for the delay period prior torenewing the feed wire drive is formed of variable capacity 236,resistor 33, tube 253 and control relay CR-Q. Therefore, before anyoperation of the system as a whole, each of these timer circuits must beadjusted by setting the'capacitors IIB, IESE and 250 to determine theproper time interval for each of these periods.

Switch 3l 6 3! i is a double-pole, double-throw switch that is used toadapt the circuit to either cam or overall timer operation, one portionof the switch being open when the other is closed. For cam operation 2l?is closed and 316 open; for overall timer operation 3l? is open and 3HEis closed. Assuming that the work is in position and `that the weldinghead is now located over` the point at which it is desired to begin, themulti-arm switch having arms 262, 280 and 282 is moved to the upper orweld position. Manual switch 222 is closed to cause the weld rod or wireto feed slowly toward the work. This wire feed motor 234-236 has itsfield 235 connected directly across the exciter 228, and, assuming thatthe three pole control switch 262, 233, 282 is in its uppermostposition, a circuit to the armature 235 of the wire fee-d motor may becompleted as follows: welding supply line 222, line 252, armature 238,line 2513, normally closed contacts Clt-41, line 256, armature 25S ofthe control exciter motor, line 236, switch 282-262, manually operableinch switch 212, resistor 2716, line 214 to one side of shunt 2li-5 insupply line 233. The direction and speed of the wire feed motor isdetermined by the voltage generated by exciter 258 and the voltageacross the arc 246i. The voltage of the exciter 258 is, of course,adjustable through movement of arm 292. rlhe voltage of the arc isopposed to the Voltage of the exciter 258, and when the arc voltage isgreater, the wire feed motor will feed the wire toward the work.Conversely, if the exciter voltage exceeds the arc voltage, then thewire motor reverses and moves the wire back away from the work. Abalance between the voltages occurs at a proper distance for welding,and as the wire burns away, tending to increase the distance and the arcvoltage, this voltage increase will affect the drive to bring the wiredown to the same distance. At one phase of the cycle the eifect of thevoltage difference may, of course, be modied or reduced by theintroduction of resistance into the control circuit to slow down thespeed and this is accomplished by the introduction or removal ofresistance 273.

With the exciter 228-233 operating, there is some voltage applied to thewelder eld coils through resistors 322, 324 and 328, which produces somevoltage across the arc gap sur'ucient to energize the wire feed motorbut not enough aaaiec to weld. This voltage, since it exceeds theexciter voltage 258, causes the wire motor to be energized by holdingdown switch 272 and the welding wire is brought down into contact withthe work. This push button shorts out the control relay contacts (3R-22and CER-|31, as well as wire speed control potentiometer 210 throughwhose setting the speed of wire feed during subsequent automatic wireinching operations is determined.

The main switch 16-298 is now closed, which completes the circuit to theoverall timer I8, which closes its contacts 'I4 to time the completeoperation. The closure of contacts 14 energizes the grid unblockingtransformer 36 by completing a circuit from power line 4, line 38,primary 3d, line 32, line 18, normally closed contacts CR-li, line l2,contacts 14, line 'i6 to power line 2. Tube 52 and its associatedcircuit forms a fourth timer circuit, which may be identified as theinterval timer, and by this is intended the total time for one weldcycle including delay spacing time; in other Words, from the be-yginning of one weld to the beginning of the next in Order. Upon theenergization of transformer 36, which blocks or bucks transformer 42,which has been blocking tube 52, the grid circuit -to tube 52 is openedand the RC time circuit 58-56 will now control the tube. After the timeperiod determined by this RC circuit, the tube 52 will conduct and thisenergizes relay CR-2 through an obvious plate circuit. The energizationof coil (2R-2 causes the closure of its contacts CR-Zi and CR-22. Theclosure of the rst set of contacts completes an obvious circuit throughrelay coil CRA to energize the same. This opens the normally closedcontacts CR-I 1, and in so doing again breaks the circuit to the primary34 of the grid unblocking transformer 3t`, thus allowing transformer 42to block tube 52 and again deenergize coil CR-2. When this occurs, itscontacts CR-21 again open to complete the cycle and deenergize relaycoil CR-l. The interval timer, therefore, acts automatically to energizerelay coil CR-Z at regular intervals as long as the overall timer l8maintains its contacts 'I4 closed.

When relay coil CR-Z was energized, as well as closing contacts CR-21,to provide the above operation, it simultaneously closed contacts CR-Zz,which completes an obvious circuit through relay coil CR-ii and normallyclosed contacts CR-91- Upon energization of relay coil CRf-S, contactsCR-z complete a holding circuit to maintain it in circuit and locks thecoil in. It also closes a set of contacts CIR-6s, which completesenergizing circuits for coils TDR-i and (3R-ll, since switch 316 isclosed. Relay coil CR-H closes hold-in contacts CR-i l1, which locks inboth CR-i i and TDR-l, and simultaneously closes CR-iiz, which completesa circuit to the flux hopper valve and energzes the same to feed flux tothe weld area. After a short interval, relay coil TDR-i pulls in toclose contacts TDR-l1 and completes a circuit through the main relaycoil MR. This circuit through the main relay may be traced as follows:line 238, Vline 28|, switch 25W-2nd, line 288, switch 29S or 3H' (switch298 if the overall timer is being used or switch 3H if the cam timer isused), line 338, switch 3532, which is a normally closed cam actuatedswitch, switch 384i, which is an emergency stop switch, line Bt,contacts TDR-l line 3538, resistance 309, MR relay coil and main line232.

Turning back for a moment to the last set of contacts operated by relaycoil CR-B, its energization lastly closes contacts CR-Gi, whichcornpletes an energizing circuit for relay coil CRP3. The energizationof relay coil CR- in turn actuates a plurality of contacts. The closureof contacts (3R-32 thereby completes a circuit through the exciter fieldcoil 298 since contacts MR2 in series therewith have been closed by theenergization of the main relay. n like manner the closure of contactsCPV-33 causes the field relay FR and relay coil CR-lZ in paralleltherewith to become energized and the closure of contacts CPs-31 shortsout the wire feed speed control 270. The closure of contacts FR; byenergization of coil FR shunts out field resistors 322, and 324inserting adjustable resistance 33t in parallel therewith to place thefull exciter voltage across the welder eld 32;- and the control rheostat32B. Simultaneously the closure of contacts CR-I22 complete a circuit tothe wire feed motor as follows: line 2M, contacts CRI-122, contactsCR-31 (previously closed), switch 26d-252, line 268, armature 25S, line256, normally closed contacts CER-fn, line 254i, armature 23S, and line252. This applies full wire feed speed, since variable resistor 278 isnot now in the control circuit and this speed and direction arecontrolled by the arc voltage as explained. Contacts (3R-i2; arenormally closed and upon energization of the relay open to break thecircuit through relay coil CR-I 3 and lieep it from being damaged by thewelding voltages.

order to move the work relative to the welding head, two relays (IR-5and CR- are provided. While the character cf such motion may be anydesired, rotary motion has here been referred as exemplary and thereforemotor 224 is described as turning a turntable, though it may also beused to provide any other motion. This motor is energized when relayCR-5 is energized, which closes contacts CR-51, CPs-52 and CR-Ba. RelayCR-S is in turn controlled by either relay CR-i or by a manual switch86, which is in parallel with contacts CR-ii. In the circuit controllingrelay CR-5 there is a switch 88, which is a toggle switch mounted in thecontrol panel, which, when it is open, deenergizes the motor 224completely when its use is not desired.

At this point, therefore, the table is moving to move the worl: past theend of the weld rod or wire, full welding current is on, the wire or rodfeed is energized to feed the wire toward the work, iiux is being feddown on the arc section to submerge the same, and the whole sequence isbeing timed by control circuits.

The time control circuit for the weld time period is that associatedwith tube 22 and includes the RC time circuit iid-H6 and relay CR-l.This circuit is permitted to go into action by the energization ofunblocking transformer |88. The circuit to primary |84 of thistransformer may be completed either through contacts CPV-t2 or Clt-22,as is obvious from Fig. l. Referring to the preceding description, itwill be recalled that relay (5R-2 is energized for only a short time,which would initially energize the primary i4. However, it alsocompletes the circuit of relay coil CR-, which closes its hold-incontacts (3R-52,v and this maintains the transformer circuit complete aslong as they are closed and CPV-22 may drop out. The work, therefore,proceeds past the weld wire and the weld continues for a timepredetermined by the values of resistance H4 and adjusted condenser Ii6. At the end of that time the tube unblocks and conducts energizingrelay GRf-I in the plate circuit through an obvious circuit. Coil CR-lcloses two sets of contacts, first CR-ii, which energizes relay coilCRf-Q, which in turn opens normally closed contacts CB1-iii to open themotor armature circuit of the wire feed motor to stop any further feedof the same, and second, contacts CR-lz, whose closure energizes gridunblocking transformer i133 of the burn off timer circuit of tube it tostart that circuit.

At this point the table is still moving, the wire feed with respect tothe table and work has stopped, but the welding current remains on toburn ofi the end of the wire sufciently far enough back to make a cleanend, prevent dribbling of particles, and also any scraping of the end onthe work over that area that it is desired to skip.

After a time period determined by the RC circuit !58-iii, tube it@unblocks and conducts, which energizes relay CRI-8 in the plate circuitthereof. Normally closed contacts CR-Si are opened by the energizationof CR-, which deenergizes relay coil CR-S, this in turn opens contactsCRf-Bz, which breaks the circuit to the control exciter field directlyand also opens contacts CR-Ss, which deenergizes relay coil FR, whichcauses contacts FE1 to open and reinsert resistance into the welder eldcircuit. This drops the voltage across the arc to a low value, dependingupon the value of the resistors. Relay CPU-l2, in parallel with relayFR, is likewise deenergized by the opening of relay CRPSS and thisallows normally closed contacts CRf-iZi to close and again energizerelay CR-i.

The energization of relay coil CR- also closes contacts CR-82 toenergize unblocking transformer It@ for tube 23%. After a suitable delayas determined by RC circuit iet-2ML the tube 204 will conduct and causeenergization of relay coil CRF@ in the plate circuit of tube Zli. Thistime delay circuit is incorporated to provide a time delay in againfeeding the wire toward the work for the next weld. When CRA] becomesenergized it opens normally closed contacts (JR-91, which results inopening the circuit for relay coil CR-E. The deenergization oi CR-starts a chain of sequential operations which deenergizes tubes I22, ldand 2cd in order. The opening of contacts CR-62 deenergizes unblockingtransformer |06 and tube l22 ceases to conduct, deenergizing relay CR-.In like manner the opening of contacts CR-lz causes tube it@ to blockand relay CR- to become deenergized. The same sequence of events followsfor the last time delay circuit in which tube 26d becomes nonconductiveand relay coil CR-Q drops out, which closes again normally closedcontacts CR-Sir to place the system in condition to repeat the wholecycle.

The deenergization of relay coil CR-i also opens contacts CR-'li whichcause relay coil CR- to become deenergized and normally closed contactsCR-li again close, completing the circuit for the armature of the wirefeed motor as previously traced, except that it now is through contactsCEE-|31 which are closed due to the energization of coil CR-i3 whenrelay CR-IZ was deenergized. The wire will then start to feed down untilit contacts the work, the speed with which it moves being determined bythe setting on wire speed control potentiometer 2li). Upon contact ofthe wire with the work the voltage drop across the welder will go toapproximately zero and since the relay coil CPV-i3 is dependent on thisvoltage, it will drop out, opening the wire feed armature circuit atCR-I3i. as just indi- 12 cated, and the feed will stop. Relay (JR-I3 isadjusted to open at a low voltage, such for example as Ll volts, so thatit will still drop out even if poor contact is made, and thus preventinching down of the wire, which might result in increase ing thepressure of the wire against the work to a point beyond optimum arcinitiating conditioni In order to more clearly describe the operation ofthe wire feed as controlled by the wire feed motor, there is includedFigure 3, which is an oscillograph of the wire motor armature voltagethrough the welding cycle and the arc voltage taken simultaneouslytherewith on a double recorder. The curves shown in this figure arereproductions of actual curves run on the equipment. The various timeintervals have been identified at the bottom of the figure and it willbe noted that the datum lines are curved to accommodate the double penrecorder, and while some points may not appear to be in the samevertical alignment to indicate the same time instant, it will be foundthat they are the same distance from the curved vertical line andtherefore occur at the same time.

At point A the wire is in close proximity to the work having been fed tothat location at the end of the previous cycle and the full weld poweris applied. The arc voltage isllow as compared to the voltage of exciter25S and the rst result is that the motor armature voltage is reversedand the wire backs away from the work as shown by the downward peak lion the upper curve. The arc voltage rises to balance the exciter voltageand reaches a substantially constant value as shown on that portion Q2of the lower curve and at point B the motor armature circuit is `brokenby the opening of contacts CR-i, and the upper voltage curve decays topoint C. lThis is the burn-off time and the welding power remains on,which increases the arc voltage to a peak 404. At this point C with thearc voltage high if the circuit to the wire motor armature wasimmediately closed a high voltage would be applied to the motor armatureto feed the wire toward the work and the speed would be so great thatthe end of the wire would hit the work and probably buckle or bend.Therefore, a short delay time is provided from C to D before the circuitof the motor armature is again closed, and it will be noted that bypoint D the arc voltage has decreased considerably along the line ofdecay following cutting off the main welding power. From point D on thearc voltage decays away until the next cycle.

At point D, however, the motor armature circuit is closed to feed thewire again down toward the work, and the armature voltage is shown asincreasing to the right of point D. When the wire reaches a point atwhich the low voltage still across the arc has dropped to say fourvolts, relay CR-i drops out opening contacts CR-l3i and the wire feedcircuit is disabled until the beginning of the next cycle at point A.The speed at which the wire is fed during the time period followingpoint D is dependent upon the setting of the potentiometer 27B. Thispotentiometer is not in the control circuit during the weld period, ascontacts CR-31 and CR-i22 are closed to shunt the same.

By the present design two dimculties in the manipulation and handling ofthe Wire rod feed have been eliminated. The iirst of these was thesticking or freezing of the electrode or wire when starting the arcwhile traveling. The reasons for this difficulty are, too heavy pressureof the rod or wire against the work so that the arc will not start andthe electrode freezes to the work or that small irregularities on theend of the electrode from the last weld make striking the arc difficult.By again referring to Figure 3, it is noted that at point e534 the arcvoltage is high and if the armature is connected into the circuit atthis point the motor will acquire such speed that the wire will hit thesurface of the work with sufcient force to buckle the same rather thanstop at its proper place for the next weld. The delay time was thereforeincorporated in the control circuit to permit the arc voltage to dropfrom point C to D, at which point the applied voltage will be proper tofeed the wire toward the work at a reasonable speed. When the wire justmakes contact with the surface of the work, it should stop, and this isaccomplished by causing relay (JR-i3 to drop out when the voltagebetween the wire and work falls to a predetermined value; as an example,it was found that if this relay dropped out at 4 volts the operation wasSatisfactory. The utilization of the burnoif of the end of the wire lefta smooth rounded end, which overcame the second reason for sticking atthe start of the weld.

The second of the difficulties mentioned above that was overcome by thissystem is the sticking, freezing or dragging of the weld rod or wire atthe end of each weld. rlhis was overcome by the inclusion of a periodwithin which the wire feed is stopped but during which the weldingcurrent remains on so that the end of the wire will burn back before thewelding current is discontinued. This leaves a smooth rounded end on thewire spaced from the work so that it will not drag over it and preventthe wire end from being trapped by the molten metal when the weldingcurrent is cut oif.

The system has now completed one weld along the junction area, has movedover a skip area, and has been readjusted to start again on a new weld.This next weld is triggered off by the interval timer circuit associatedwith tube 52, which as previously mentioned automatically operates atregular intervals as long as the overall timer i is energized, eachinterval being of sufficient length to permit a weld area and spacing totake place. Assuming, therefore, that the proper time has passed, thenthe interval timer tube 52 will now conduct and relay CR-Z will closeits contacts (3R-22 to energize the relay CR-Q and the whole cycledescribed above will loe again repeated, and this will take place `foras many individual welds as are desired. When the total line or distancehas been covered, then the overall timer will operate to open itscontacts 14, which deenergizes the interval timer so that it will nolonger be operative, and thus shut down the whole system. It will beobvious that if the overall timer becomes deenergized during part of thesequence of operation, the system will complete its part cycle andclear, stopping when all is in readiness for a new cycle. When theon-oif switch i6 is opened, the overall timer I8 is reset for a newtiming operation, and since switch 296 forms a part of and ismechanically connected to and moves with switch I6, that opens also todeenergize relay coils TDR-I and CR-l i. This closes the flux air valvelil-i2 and stops the liow of flux to the part. At this point it is alsodesirable to move the wire back up out of the way so that the partwelded may be taken from the machine. The multi-arm switch 252, 28B, 282is moved to its lower position, which is labelled up, and this placesarmature 236 di rectly across the exciter armature 258 through anobvious circuit and so the former runs at full speed to retract the wireas long as the switch is left closed in this position. The part that hasbeen welded may now be removed from the machine and another new one tobe welded may be placed thereon and the system again started.

Instead of having the sequence of events controlled by interval andsequence timers 52 and I3, the system may as easily be controlled by camoperated switches actuated by movement of the work carrying supportitself. The two switches which initiate and stop the cycle in this casewill be micro-switches 98 and 302, the first of which it will be seen isin shunt to switch CIR-22 and, therefore, makes the operation of CR-2unnecessary. The spacing of cams which momentarily close microswitch 98determine the interval time. Cam operated switch 3D2 cuts the wholesystem off at the completion of the welding on a given part. The switch3l1 should be closed and switch 3| open at the beginning of the weldingprocess if Icam switches are to be used, and switch 298-46 should beopen. Push button 3M is merely an emergency stop switch and deenergizesthe system completely on operation.

We claim:

l. In welding means for producing a plurality of spaced welds betweenparts to be Secured together, a supply of Weld rod, means for feedingthe weld rod toward the parts, means for moving said parts continuouslypast the rod, means for intermittently applying welding current to therod, timing control means to deenergize the weld rod feeding means priorto the cessation of welding current, a second timing control means todelay reenergization of the rod feeding means for a predetermined timeafter the weld current has ceased to flow, and control means to causesaid rod feeding means to operate at a lower than normal speed to causethe rod to approach the parts prior to the termination of the intervalin which the welding current is not applied to the rod.

2. In welding means for producing a plurality of spaced welds betweenparts to be secured together, a supply of weld rod, means for feedingthe weld rod toward the parts, means for moving said parts continuouslypast the rod, control means for periodically applying Welding current tothe rod, timing control means for the weld rod feed to deenergize thefeeding means prior to discontinuance of the main welding current, and asecond timing control means for the weld rod feed to delayreenergization of the same for a predetermined period afterdiscontinuance of the weld current but apply it prior to re-applica tionof the welding current.

3. In welding means for producing a plurality of spaced welds betweenparts to be secured tcgether, a supply of weld rod, means for feedingthe weld rod toward the parts, means for moving said parts continuouslypast the rod, control means for periodically applying welding current tothe rod, timing control means for the weld rod feed to deenergize thefeeding means prior to discontinuance of the main welding current, asecond timing control means for the weld rod feed to delayreenergization of .the same for a predetermined period afterdiscontinuance of the weld current, and means to again deenergize theweld rod feeding means when the arc voltage falls to a predeterminedvalue prior to the next successive weld.

'4. A method for securing together parts by a plurality f spacedintermittent welds utilizing a weld rod fed toward the parts includingthe steps of feeding the rod until it contacts the parts, applyingwelding voltage to the rod to produce an are, continuously moving theparts with respect to the rod, stopping the feed of the rod apredetermined time prior to the cessation of the welding voltage toallow the rod to burn on" and provide a space between the rod end andthe parts so that it will not engage the parts during that period thatit moves thereover and no welding voltage is applied, delaying anyfeeding of the weld rod toward the parts for a predetermined time andthen feeding the rod toward the parts at a lower than normal speed untilengagement is made prior to the next application of welding power.

5. In welding means for securing parts together, a weld rod, means forautomatically feeding said rod toward the parts, means to move the partswith respect to the weld rod and a plurality of interlocked timing andcontrol circuits for intermittently applying welding voltage to the rod,feeding and stopping the rod to produce a series cf spaced welds betweenthe parts, said application of power to the rod interval extending intosaid interval for stopping cf weld rod feed, delaying again feeding thered after the breaking of the welding voltage for a predeterminedinterval and providing a predetermined time following the feeding downof the rod before reapplication of welding voltage.

6. In welding means for securing parte together, a weld rod, means forautomatically feeding said rod toward the parts, means to move the partswith respect to the weld rod and a plurality of interlocked timing andcontrol circuits for intermittently applying welding voltage to the rod,feeding and stopping the rod to produce a series of spaced welds betweenthe parts, said application of voltage to the rod interval extendinginto said interval for stopping of weld rod feed, delaying again feedingthe rod after the breaking of the welding voltage for a predeterminedinterval, feeding the rod toward the parts at a predened lower thannormal speed and providing a predetermined time foilowing the feedingdown of the rod before reapplication of welding voltage.

'7. In welding means to secure parts together' along a common junctionline by a series of spaced welds, a supply of welding rod, means to movethe parts continuously past the welding rod, means for feeding said weding rod toward the parts, a supply of welding current, switching meansand control circuits interconnecting said supply rod, means for-feedingthe rod and the parts, timing means to initiate each of a plurality ofsuccessive weld cycles, a second timing means controlled by the first toapply welding current to the weld rod and parts for a prescribed time, athird timing means to deenergize the weld rod feeding means prior to theopening of the welding circuit and controlled by the second timing meansand a fourth timing means to provide a delay before reenergization ofthe rod feeding means and controlled by the third timing means.

8. In welding means to secure parts together along a common junctionline by a series of spaced welds, a supply of welding rod, means to movethe parts continuously past the welding rod, means for feeding saidwelding rod toward the parts, a supply of welding current, switchingVmeans and control circuits interconnecting said supply rod, means forfeeding the rod and theA parts and a plurality of sequential timingcircuits each controlling the next in order connected to the controlcircuits to initiate a welding cycle, energize the welding circuit,deenergize the means for feeding the welding rod, and provide a delayfollowing cessation of the welding current before a reenergization ofthe weld rod feeding means in order for each of the spaced welds.

9. In welding means to secure parts together along a common junctionline by a series of spaced welds, a supply of welding rod, means to movethe parts continuously past the welding rod, means to feed said weldingrod toward the parts, a source of power, an adjustable timing controlmeans interconnecting said source, rod, parts and the means for feedingthe rod to control the length of the periods for the feeding thereof,and a second adjustable timed control switching means to control thetermination of the application of full welding current to the rod andparts and to interrupt the same, said second timing means beingtriggered by said first to provide an adjustable burn-oif interval.

19. In welding means to secure parts together along a common junctionline by a series of spaced welds, a supply of welding rod, means to movethe parts continuously past the welding rod, means to feed said weldingrod toward the parts, a source cf power, an adjustable timing controlmeans interconnecting said source, rod, parts and the means for feedingthe rod to control the length of the periods for the feeding thereof, asecond adjustable timed control switching means to control thetermination of the application of full welding current to the rod andparts and to interrupt the same, said second timing means beingtriggered by said first to provide an adjustable burn-off interval, anda third adjustable timing control means to control the reapplication ofpower to the weld rod feeding means triggered by the second timing meansto iprovide a delay interval after the welding power is removed beforethe weld rod may again be fed.

11. In welding means to secure parts together along a common junctionline by a series of spaced welds, a supply of welding rod, means to movethe parts continuously past the welding rod, means to feed said weldingrod toward the parts, a source of power, an adjustable timing controlmeans interconnecting said source, rod, parts and the means for feedingthe rod to control the length of the periods for the feeding thereof, asecond adjustable timed control switching means to control thetermination of the application of full welding current to the rod andparts and to interrupt the same, said second timing means beingtriggered by said first to provide an adjustable burn-ofi interval, athird adjustable timing control means to control the re-application ofpower to the weld rod feeding means triggered by the second timing meansto provide a delay interval after the welding power is removed beforethe weld rod may again be fed and a main adjustable timer control system-connected to the circuit to determine the complete time for one weldcycle, said main timer control initiating the operation of said firstadjustable timing means and conditioned for energization by the thirdadjustable timing means so that a completion of the various portions ofone welding cycle places the control system in condition to be re-cycledly the next master control pulse from the main lmer.

17 12. In welding means for securing parts together, a weld rod, meansfor automatically feeding said rod toward the parts, means to move theparts continuously with respect to the Weld rod and a plurality ofinterlocked timing and control circuits for intermittently applyingWelding voltage to the rod, feeding and stopping the rod to produce aseries of spaced Welds between the parts, delaying for a predeterminedinterval feeding the rod ater breaking or" the welding voltage supply,feeding the rod toward the parts at a lower than normal speed andproviding a predetermined time period after the rod has reached a properposition with respect to the parts before reapplication of the weldingvoltage.

STUART M. SPICE. WILLIAM F. WILLIAMS, JR. WILBUR E. MOEHRING.

References Cited in the 111e of this patent UNITED STATES PATENTS NumberNumber Name Date Kramer July 17, 1917 Whiting Sept. 16, 1924 Jefts Feb.5, 1929 Caldwell Novi. 10, 1931 Burgett Dec. 12, 1939 Levy Oct. 21, 1941Clapp Oct. 28, 1941 Kratz et al Feb. 8, 1949 FOREIGN PATENTS CountryDate Great Britain July 28, 1932 Germany May 30, 1938

